The work of a turbocharger depends on energy received by a turbine from exhaust gas. For this reason, in a low rotation region in which the amount of exhaust gas from an engine is small, the effect of a turbocharger is small. Thus, a supercharging system capable of performing supercharging even in a case in which the amount of exhaust gas is small by including a turbocharger and an electric compressor in an air supply passage has been researched. In a case in which a supercharging command is received from an engine when the amount of exhaust gas of the engine is small, a control device of a supercharging system first increases the flow rate of intake air by driving an electric compressor. At this time, in the electric compressor, instant acceleration is required.
In addition, in Patent Document 1, a circuit including means for raising a voltage for increasing the speed of an electric motor and means for performing weak magnetic-flux control is disclosed.